U.S. Army soldiers from A Company, 3rd Battalion, 7th Infantry Regiment, search one of Saddam Hussein's palaces damaged after a bombing, in Baghdad Monday, April 7, 2003. Coalition soldiers took over key buildings Monday, as gunfire and explosions thundered in many parts of the battered Iraqi capital. (AP Photo/John Moore)

In a fresh attempt to kill Saddam Hussein and hasten the end of the war, a U.S. warplane dropped four powerful bombs on a suburban Baghdad apartment building Monday afternoon.

The 2,000-pound, satellite-guided JDAM explosives launched by a lone B-1B bomber demolished what U.S. officials called a "leadership target" in the upscale Mansour neighborhood.

Definitive word on whether Hussein and his sons Odai and Qusai were at the site -- as an intelligence tip indicated -- could take some time. But early today, senior U.S. military officials speculated that Hussein had finally been hit.

One told the New York Times that "intelligence indicated that there would definitely be senior leadership, including Saddam Hussein, at a meeting in that structure," which he described as a house. "But we just can't absolutely confirm . . . that he's dead."

Rescue workers said the bombs, known formally as Joint Direct Attack Munitions, carved out a 60-foot-deep crater and killed as many as 14 people, none of whose names have been released.

Hussein was also the intended quarry in a U.S. bomb and cruise missile attack on the war's opening night, March 20. Ever since, there has been intense speculation on whether he survived. But his subsequent appearances on videotape have led most intelligence officials to conclude that he did.

The new "decapitation" bid came during a day in which American soldiers poured into Baghdad and British troops declared that Hussein's regime was "finished" in Basra.

Today, the U.S. military presence in Baghdad seemed to grow more conspicuous and sure-footed by the hour. American warplanes circled over the city as two U.S. tanks took up positions on a bridge over the Tigris River in central Baghdad, exchanging fire with Iraqi soldiers.

Not far away, flames and plumes of smoke spewed from some multistory buildings apparently hit in recent air strikes.

Earlier, however, allied officials cautioned against overconfidence.

Hours after American troops and tanks slashed into Baghdad and seized two of Hussein's ornate palaces in a Monday morning operation that left between 600 and 1,000 Iraqi fighters dead, Defense Secretary Donald Rumsfeld said that a declaration of victory would come "later, rather than sooner. . . . Without having really done a good deal of work around the country. . . . (such a declaration) would be inappropriate."

But there was a strong sense that the regime had sustained tremendous damage in a weekend air strike near Basra. Believed to have been killed were not only Ali Hassan al-Majid, the infamous "Chemical Ali" who gassed innocent Kurds in the late 1980s, but -- according to the Washington Post -- also Tahir Jalil Haboush, the head of Hussein's feared secret police, known as the Mukhabarat.

The Americans made clear after Monday morning's surge into the capital that they had no intention of leaving.

After obliterating with a tank round a 40-foot bronze equestrian statue of Hussein and engaging in firefights all day, elements of the 2nd Brigade of the 3rd Infantry Division spent the night in a portion of the dictator's new presidential palace on the west bank of the Tigris.

Col. David Perkins, the force's commander, told reporters: "We had a lot of suicide attackers today. These guys are going to die in droves. . . . They keep trying to ram the tanks with car bombs."

More than 1,000 Marines who had fought their way across the Diyala River, a tributary of the Tigris, made camp where they could in the devastated neighborhoods of southeastern Baghdad.

By late in the day, American tanks and amphibious assault vehicles were backed up in miles-long lines at two bridges, waiting to enter the capital on heavy military rafts or over pontoon bridges.

U.S. officials said the mission of Perkins' soldiers was to conduct attacks against key government ministries and try to hunt down top regime figures.

The officials added that they now believed, based on communications intercepts, that Qusai Hussein, the dictator's younger son, was in charge of the Iraqi military effort. They also suggested that the leadership was being given overly optimistic assessments by commanders afraid to deliver bad news because of harsh retribution that has been meted out in the past by the regime.

As the Americans kept the pressure on, there were also setbacks to absorb.

Although the allies have strived to minimize civilian casualties, the toll continued to mount in sprawling, populous Baghdad. The International Committee of the Red Cross (ICRC) said the number of injuries in the capital has risen so high that hospitals have stopped keeping count.

KEY ARMY CENTER HIT

Iraqi street-fighting units killed at least two soldiers from the 2nd Brigade, and an Iraqi missile hit the unit's tactical operations center on the southern outskirts of Baghdad, killing at least two U.S. soldiers and wounding 15.

U.S. officials were trying to determine whether the Iraqis simply got off a lucky shot or had detected electronic emissions from the operation center's radios and other communications equipment.

Eight journalists have died in Iraq covering the conflict. In another incident, Iraqi gunmen kidnapped two Polish journalists at a checkpoint near Hilla, about 80 miles south of Baghdad.

Two Marines were killed and two were injured in the battle for eastern Baghdad after an artillery shell hit their armored personnel carrier.

Maj. Gen. David Petraeus, commander of the 101st Airborne Division, which took Najaf and Karbala after difficult fights, described Hilla as "a black hole" of Iraqi resistance.

"We had a hell of a fight on the road into there the other day," he said. Close to 300 civilians were killed or injured in the operation, the ICRC said.

State television repeated urgings by Hussein first broadcast on Sunday for Iraqis to join any military unit they could find.

There still seemed to be many in Baghdad willing to fight. The city's streets were filled with a mixed bag of soldiers carrying rifles and grenade launchers, civilians and Fedayeen Saddam militiamen, who darted around in mud- caked pickups to conceal themselves from the air.

One of the day's most intriguing developments was the announcement by Pentagon officials that 13 drums discovered at an agricultural facility near Hindiya on Friday had tested positive for the nerve agents sarin and Tabun, and the blister agent lewisite.

If confirmed by more extensive testing, it would be the strongest sign yet that Iraq has an arsenal of banned weapons. The United States and Britain have cited the issue as their primary justification for waging war against Hussein.

U.S. officials spoke cautiously about the find, reluctant to make too much of what could turn out to be a "false positive." They said a chemical and biological weapons search team was on its way to the Hindiya complex for further tests.

The officials also said they were investigating reports of another alleged weapons site near Baghdad. National Public Radio reported on Monday that coalition forces had found about 20 surface-to-surface missiles armed with nerve gas there.

BUSH, BLAIR MEET

In Northern Ireland, meanwhile, President Bush and British Prime Minister Tony Blair conferred in person for the third time in less than a month, attempting to bridge their differences over how to shepherd a postwar Iraq.

Bush favors a primary role for the United States in both the reconstruction of the country and devising a form of government. Blair wants the United Nations to be a major participant, a stance being partly driven by public opinion in Britain.

A major point of contention is the British desire for fresh leaders to emerge in Iraq. The United States thinks a governing structure must be set up quickly, which increases the chances that it will be dominated by expatriate politicians who lack popular support.